Controller for electric motors.



No. 768,711. PATENTED AUG. 30', 190.4.

- P. G. WATKINS.

CONTROLLER FOR ELECTRIC MOTORS.

APPLICATION FILED NOV. 20, 1903.

N0 MODEL.

2 SHEETS-SHEET 1.

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. M after/1121f PATENTED AUG. 30, 1904.

I. O. WATKINS. CONTROLLER FOR ELECTRIC MOTORS.

APPLICATION FILED NOV. 20, 1903 2 SHEETS-SHEET 2.

NO MODEL.

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Patented August 30, 1904,

PATENT OFFICE.

FRANK O. ATKINS, OF VALLEJO, CALIFORNIA.

CONTROLLER FOR ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent No. 768,711, dated August 30, 1904.

Application filed November 20, 1903. Serial No. 181,968. (No model.)

To (all whom it may concern:

Be it known that 1, FRANK O. WATKINS, a citizen of the United States, residing at Vallejo, in the county of Solano and State of California, have invented new and useful Improvements in Controllers for Electric Motors, of which the following is a specification.

This invention relates particularly to means for automaticaly controlling the starting and stopping of an electric motor, said controlling being effected by a pressure-gage acting to open or close the circuit of the motor-according to the pressure, usually in a tank or reservoir, created by the operation of a pump or similar device driven by the motor.

The invention can also be applied to a boilerfeeder to control the pump thereof according to the pressure in the boiler, also in connection with hydraulic elevators and in various other utilizations.

The device is illustrated in the accompanying drawings, in which Figure 1 is a diagrammatic View illustrating the apparatus. Fig. 2 is an elevation of a pressuregage containing the contacts governing the switch-circuit, and Fig. 3 is an enlarged plan view of the switch in the shuntcircuit which contains the solenoid controlling the main switch.

Referring specifically to the drawings, 6 and 7 indicate the lines of the main circuit containing the motor which is to be controlled. In the line 8 of the shunt-circuit derived from the main circuit is a high-resistance solenoid 9, the core of which controls the main switch 10 in the main circuit. This switch is actuated by making and breaking the shunt-circuit according to the movements of the pointer-arm in the pressure-gage 11, to close one or the other of circuits through electromagnets 12 and 13, which actuate a switch 14:1I1tl16 shunt. A branch 15 leads from the main line to contact-pieces 15 in the gage 11. These contact-pieces are flexible strips of metal and are positioned to respectively close with contact-pieces 15 by the action of the vibrating lever 11 of the gage, which is preferably of the common Ashcroft type. A piece of insulation 11", carried by the lever, strikes the contact-strips. Each pair of contact-pieces is supported upon insulating-blocks 16, which are pivoted to the back plate of the gage and may be adjusted to vary the time of contact according to the maximum or minimum of pressure desired. hen set as desired, they are fixed by screws 16, which extend through slots 16, formed in the blocks. From each of the contacts 15 a wire leads to a carbon 17, carried by one arm of a lever 18,which is pivoted at 18, and the other arm of which is curved to project in the way of an insulating-block 1 1, carried by the switch-bar 1 1. This switch-bar slides over contacts 8 at the ends of the respective lines 8- and 8 of the shunt-circuit, and when the switch-bar is in contact with said blocks it closes said circuits and actuates the solenoid 9 to close the main switch 10, and consequently the main circuit.

The movement of the switch-bar 1 1 is produced by the electromagnets 12 and 13, either of Which may be actuated according to the contacts at the gage. One end of each magnet-coilis connected to a carbon block 17 opposite the carbonl'Y, and the other ends of the magnet-coils are connected by wires 19 to the line 8 of the shunt-circuit. The purpose of the carbon contacts is to prevent arcing at the gage-contacts by breaking the circuit at the carbon instantly or before it is broken at the gage-contacts. This is done by means of the movement of the switch-bar 1a, which strikes the tails of the levers and breaks the circuit through the operating-magnets.

In operation, assuming that the parts are as shown in Fig. 1, which will be the position when the pump is operating, the shunt-circuit is closed, and consequently also the main circuit. When the maximum pressure desired is reached, the gage-lever will close the contacts 15 and 15 on the side containing the magnet 12, and current will flow through said magnet, drawing the armature switch-bar 14 and opening the switch at 8. This breaks the shuntcircuit and allows the switch 10 to drop and break the main circuit, thereby stopping the action of the motor. At the same instant the block 1 1 strikes the lever 18, which breaks the contacts at the carbons, producing the are there, if anywhere, so that when the contact in the gage is broken there will be no current. l

W hen the minimum pressure is reached, the reverse action takes place. The gage-lever makes a contact on the opposite side and the current flows to the magnet 13, (the lever 18 on that side having dropped the carbons to c ntact when the switch-bar 14 was drawn to the other side,) which draws the switch-bar 14 and closes the contacts at 8", and consequently the sh unt-circuit, which actuates the solenoid and closes the main switch and starts the motor. At the same instant the carbon contacts at 17 and 17 are broken by the switch-bar striking the lever.

It will be seen that there is no circuit through the gage-contacts or magnet-coils except at theinstant of changing the switch, and the current is broken at the carbon simultaneously with such change. Consequently a heavy current can be used without danger of arcing in the gage, because the circuit is no sooner made than it is broken, and in breaking the arc is made at the carbon point, which can be easily renewed.

What I claim as new, and by Letters Patent, is

1. The combination with a motor-circuit having a main switch therein, and a shunt-circuit therefrom controlling said switch, of a primary switch in the shunt-circuit, oppositely-acting electromagnets controlling said primary switch, a pressure device having contacts arranged to close the circuit of either magnet according to the predetermined maximum or minimum, and means actuated by the movement of the primary switch to immedidesire to secure ately break the circuit so closed at a point other than the contacts of the pressure device.

2. The combination with the controlled circuit, and a controlling-circuit shunted therefrom and having a switch therein, of oppositely-acting electromagnets controlling said switch, a pressure-gage having contacts arranged to close the circuit of either magnet according to the pressure, and an arcing contact in each of the magnet-circuits, arranged to beopened by the movement of the switch immediately after the circuit is closed, said arcing contacts being separate from'the said pressure-gage contacts.

3. The combination with the opposite electromagnets having a switch-armature therebetween, of the pressure-gage having contacts in the circuit of each magnet and arranged to close either circuit according to the pressure, arcing contacts in each circuit, separate from the pressure-gage contacts, and levers carrying said contacts and arranged in the way of the armature and acting to open the circuit when the armature moves.

4. The pressure-gage havingthe two adjustable insulating-blocks 16 and two contactpieces carried by each, and the pressure-actuated lever Working between the blocks and arranged to close the contacts at either block.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

F. (J. WVATKINS.

Witnesses:

G. L. WINGi-IELL, S. ODLE. 

